674
S. Nandi et al. / Tetrahedron 71 (2015) 669e675
1
ꢁ1
in hexane) 0.39; H NMR (CDCl
t, 2H, J¼7.8 Hz, CH ), 3.69 (t, 2H, J¼7.8 Hz, OCH
OCH ), 3.97 (s, 3H, OMe), 4.89 (s,1H, CH C(Me)CH
CH C(Me)CH ), 7.47e7.58 (m, 2H, ArH), 8.03e8.12 (m, 2H, ArH);
C NMR (CDCl , 50 MHz) : 19.5, 31.0, 61.3, 62.7, 68.8, 74.8, 112.1,
16.7, 122.6, 122.7, 126.6, 126.7, 127.5, 127.9, 128.2, 142.4, 150.1, 151.5.
Anal. Calcd for C18 21BrO : C, 59.19; H, 5.79. Found: C, 59.40; H,
3
, 200 MHz)
d
: 1.74 (s, 3H, Me), 3.35
), 3.96 (s, 5H, OMe
), 4.99 (s,1H,
149.6; IR (liquid film):
Anal. Calcd for C20
HRMS (ESI) m/z [MþH] for C20
n
max 1619, 1516, 1477, 882, 765, 719 cm
.
(
&
2
2
H O : C, 76.89; H, 7.74. Found: C, 77.06; H, 7.93;
24 3
þ
2
a
H
b
2
25 3
H O : 313.1798, found: 313.1796.
H
a b
2
1
3
3
d
4.2.7.12. 1,2,5,6-Tetrahydro-5-methylene-4H-naphtho[2,3-d]ox-
ꢀ
1
ocine-7,12-dione (24). Yellow solid; yield 94%; mp 88e89 C; R
f
1
H
3
(40% EtOAc in hexane) 0.49; H NMR (CDCl
2H, J¼5.2 Hz, CH ), 3.63 (s, 2H, CH ), 3.85 (t, 2H, J¼5.4 Hz, OCH
.08 (s, 2H, OCH ), 5.02 (s, 1H, CH C(CH )CH ), 5.17 (s, 1H,
CH C(CH )CH ), 7.67e7.72 (m, 2H, ArH), 8.05e8.09 (m, 2H, ArH);
C NMR (CDCl , 50 MHz) : 28.2, 33.2, 71.3, 75.5, 116.1, 126.5, 126.6,
132.2, 132.4, 133.6, 133.7, 144.4, 145.8 (2C), 184.0, 184.5; IR (liquid
3
, 200 MHz)
d
: 3.09 (t,
5
.56.
2
2
2
),
4
2
a
H
b
2
2
4
.2.7.7. 2-(2-(2-Methylallyloxy)ethyl)-3-bromo-1,4-
(2% EtOAc in
: 1.56 (t, 3H, J¼7.0 Hz,
), 1.75 (s, 3H, Me), 3.33 (t,
), 3.66 (t, 2H, J¼7.2 Hz, OCH ), 3.96 (s, 2H, OCH ),
.03 (q, 2H, J¼7.0 Hz, OCH ), 4.11 (q, 2H, J¼7.0 Hz, OCH ), 4.89 (s, 1H,
C(Me)CH ), 4.98 (s, 1H, CH C(Me)CH ), 7.47e7.53 (m, 2H,
ArH), 7.99e8.10 (m, 2H, ArH); C NMR (CDCl , 50 MHz) : 15.9,16.0,
9.6, 31.3, 68.9, 70.0, 71.1, 74.9, 112.2, 117.1, 122.7 (2C), 126.5, 126.6,
27.6, 128.2, 128.6, 142.5, 149.4, 150.5. Anal. Calcd for C20 25BrO : C,
1.07; H, 6.41. Found: C, 61.29; H, 6.24.
a
H
b
2
2
13
diethoxynaphthalene (21b). Yellow liquid; yield 87%; R
hexane) 0.44; 1H NMR (CDCl
, 200 MHz)
OCH CH CH
), 1.57 (t, 3H, J¼7.0 Hz, OCH
H, J¼7.2 Hz, CH
f
3
d
3
d
ꢁ1
2
3
2
3
film):
n
max 1682, 1640, 1428, 834, 767 cm . Anal. Calcd for
C H O : C, 75.57; H, 5.55. Found: C, 75.66; H, 5.67; HRMS (ESI) m/
2
4
2
2
2
16 14 3
þ
2
2
z [MþH] for C16
15 3
H O : 255.1016, found: 255.1016.
CH
H
a b
2
a
H
b
2
13
3
d
4.2.7.13. (5Z)-1,2-Dihydro-5-methyl-4H-naphtho[2,3-d]oxocine-
ꢀ
1
7,12-dione (25). Yellowsolid; yield 91%; mp 84e85 C; R
f
(40% EtOAc
1
1
H
3
in hexane) 0.54; H NMR (CDCl
2H, J¼5.6 Hz, CH ), 4.48 (s, 2H, OCH
CHC(Me)CH ), 7.69e7.75 (m, 2H, ArH), 8.06e8.11 (m, 2H, ArH);
NMR (CDCl , 50 MHz) : 22.6, 31.3, 65.7, 75.9, 117.9, 126.3, 126.8,
3
, 200 MHz)
d
: 1.97 (s, 3H, Me), 3.66 (t,
6
2
2
), 4.78 (s, 2H, OCH
2
), 6.81 (s,1H,
13
2
C
4
.2.7.8. 2,4,5,6-Tetrahydro-7,12-dimethoxy-5-methylene-1H-
naphtho[2,3-d]oxocine (22a). Yellowliquid; yield 84%; R (10% EtOAc
: 3.24 (t, 2H, J¼4.8 Hz,
), 3.91 (s, 3H, OMe), 3.94 (s, 3H, OMe),
), 4.96 (s, 1H, CH C(CH )CH ), 5.20 (s, 1H,
), 7.47e7.54 (m, 2H, ArH), 8.03e8.11 (m, 2H, ArH);
, 50 MHz) : 29.9, 32.7, 62.5, 62.7, 74.2, 75.2, 113.4,
22.7 (2C),125.9 (2C),127.9,128.1,129.2,129.8,147.6,150.0,150.6; IR
3
d
f
132.0, 132.3, 133.7, 134.0, 139.9, 142.2, 155.5, 183.8, 184.7; IR (liquid
max 1673,1617, 1462, 1392, 839, 745, 711 cm . Anal. Calcd for
16 14 3
C H O : C, 75.57; H, 5.55. Found: C, 75.45; H, 5.69; HRMS (ESI) m/z
1
ꢁ1
in hexane) 0.59; H NMR (CDCl
CH ), 3.87 (s, 2H, CH
.94e3.99 (m, 4H, OCH
CH C(CH )CH
C NMR (CDCl
3
, 200 MHz)
d
film):
n
2
2
þ
3
2
a
H
b
2
2
[MþH] for C16
15 3
H O : 255.1016, found: 255.1017.
H
a b
2
2
13
3
d
4.2.8. General procedure for the formation of compound 27. A
mechanically stirred solution of dimethylformamide (3 equiv) in
anhydrous chloroform was cooled in ice bath while phosphorus
tribromide (2.7 equiv) was added drop-wise over a period of
15 min. The resulting white suspension was warmed to room
temperature and stirred for additional 20 min. A solution of starting
ketomethyl compound 26 (4.85 mmol) in chloroform was added
drop-wise over 10 min. Stirring was continued for 8 h at room
temperature. The reaction mixture was then poured in ice water.
Solid sodium bicarbonate was carefully added to neutralize the
acids and the mixture was extracted several times with dichloro-
methane. The organic part was then washed with cold water
thoroughly, dried with sodium sulfate and evaporated. Purification
of the residue was done by silica gel (60e120 mesh) column
chromatography yielded the bromoaldehyde 27.
1
ꢁ
1
(
liquid film):
n
max 1641, 1515, 1496, 1364, 1130, 984, 813 cm . Anal.
: C, 76.03; H, 7.09. Found: C, 76.25; H, 7.26; HRMS
Calcd for C18H
20
O
3
þ
(
ESI) m/z [MþH] for C18
21 3
H O : 285.1485, found: 285.1482.
4
.2.7.9. 7,12-Diethoxy-2,4,5,6-tetrahydro-5-methylene-1H-naph-
tho[2,3-d]oxocine (22b). Yellow liquid; yield 82%; R (10% EtOAc in
hexane) 0.65; 1H NMR (CDCl
, 200 MHz)
: 1.55 (t, 3H, J¼7.0 Hz,
OCH CH CH ), 3.24 (t, 2H, J¼5.2 Hz,
), 1.57 (t, 3H, J¼7.0 Hz, OCH
), 3.86 (s, 2H, CH ), 3.92e4.09 (m, 8H, OCH ), 4.94 (s, 1H,
C(CH )CH ), 5.18 (s, 1H, CH C(CH )CH ), 7.44e7.51 (m, 2H,
, 50 MHz) : 15.7, 15.8,
9.9, 32.6, 70.3, 70.5, 74.1, 74.9, 112.6, 122.4 (2C), 125.5 (2C), 127.9,
28.1, 128.9, 129.7, 147.6, 148.8, 149.5; IR (liquid film): max 1638,
498, 1384, 1235, 963, 828, 777 cm . Anal. Calcd for C20 : C,
6.89; H, 7.74. Found: C, 76.66; H, 7.95; HRMS (ESI) m/z [MþH] for
: 313.1798, found: 313.1797.
f
3
d
2
3
2
3
CH
CH
2
2
2
a
H
b
2
2
a
H
b
2
2
13
ArH), 8.0e8.07 (m, 2H, ArH); C NMR (CDCl
3
d
2
1
1
n
ꢁ
1
24 3
H O
þ
7
4.2.8.1. 1-Bromo-5,8-dimethoxy-3,4-dihydronaphthalene-2-
ꢀ
C
H
20 25
O
3
carbaldehyde (27). Yellow solid; yield 82%; mp 105e106 C; R
f
(10%
1
EtOAc in hexane) 0.47; H NMR (CDCl
J¼8.2 Hz, CH ), 2.59 (t, 2H, J¼7.8 Hz, CH
3H, OMe), 6.74 (d, 1H, J¼9.0 Hz, ArH), 6.84 (d, 1H, J¼9.0 Hz, ArH),
3
, 200 MHz)
d: 2.31 (t, 2H,
4
.2.7.10. (Z)-2,4-Dihydro-7,12-dimethoxy-5-methyl-1H-naphtho
2,3-d]oxocine (23a). Yellow liquid; yield 80%; R (10% EtOAc in
: 1.55 (s, 3H, Me), 3.33 (t,
), 3.58 (q, 2H, J¼7.2 Hz, OCH ), 3.90 (t, 2H,
), 3.95 (s, 3H, OMe), 3.96 (s, 3H, OMe), 5.89 (s, 1H,
2
2
), 3.71 (s, 3H, OMe), 3.77 (s,
[
f
1
13
hexane) 0.47; H NMR (CDCl
H, J¼8.0 Hz, CH
J¼8.0 Hz, OCH
CHC(Me)CH ), 7.51e7.58 (m, 2H, ArH), 8.02e8.10 (m, 2H, ArH);
NMR (CDCl , 50 MHz) : 19.6, 31.1, 56.4, 61.4, 62.6, 70.3, 110.7, 116.6,
22.6, 122.7, 126.7 (2C), 126.9, 127.9, 128.2, 140.0, 150.2, 151.5; IR
3
, 200 MHz)
d
10.16 (d, 1H, J¼1.4 Hz, CHO); C NMR (CDCl
3
, 50 MHz) d: 21.1, 21.9,
2
2
2
56.1, 56.2, 111.5, 114.5, 123.7, 130.7, 133.5, 136.9, 149.5, 152.4, 192.8.
2
Anal. Calcd for C13
H
13BrO
3
: C, 52.55; H, 4.41. Found: C, 52.71; H,
13
þ
2
C
4.55; HRMS (ESI) m/z [MþH] for C13
3
H14BrO : 297.0121, found:
3
d
297.0117.
1
(
ꢁ
1
liquid film):
for C18 : C, 76.03; H, 7.09. Found: C, 75.88; H, 7.30; HRMS (ESI)
m/z [MþH] for C18
n
max 1624, 1498, 1386, 978, 812, 782 cm . Anal. Calcd
4.2.8.2. (4-Bromo-1,2-dihydro-5,8-dimethoxynaphthalen-3-yl)-
methanol (28). Colourless oil; yield 94%; R (40% EtOAc in hexane)
: 2.38 (t, 2H, J¼7.8 Hz, CH ), 2.73 (t,
), 3.82 (s, 3H, OMe), 3.86 (s, 3H, OMe), 4.55 (s, 2H,
H
20
O
3
f
þ
1
21
H O
3
: 285.1485, found: 285.1487.
0.35; H NMR (CDCl
H, J¼7.8 Hz, CH
CH OH), 4.83 (s, 1H, OH), 6.83 (s, 2H, ArH); C NMR (CDCl
50 MHz) : 21.9, 27.1, 56.4, 56.9, 65.8, 111.9, 112.1 (2C), 124.6, 128.9,
141.5, 149.8, 151.1. Anal. Calcd for C13
3
, 200 MHz)
d
2
2
2
13
4
.2.7.11. (Z)-7,12-Diethoxy-2,4-dihydro-5-methyl-1H-naphtho
2,3-d]oxocine (23b). Yellow liquid; yield 79%; R (5% EtOAc in
: 1.47e1.57 (m, 6H,
), 1.91 (s, 3H, Me), 3.32 (t, 2H, J¼5.0 Hz, CH ), 4.02 (t, 4H,
J¼7.0 Hz, OCH ), 4.48 (s, 2H, OCH ), 4.91 (s, 2H, OCH ), 6.87 (s, 1H,
CHC(Me)CH ), 7.42e7.52 (m, 2H, ArH), 7.99e8.12 (m, 2H, ArH);
NMR (CDCl , 50 MHz) : 15.9, 16.0, 22.0, 31.1, 66.7, 70.9, 71.8, 76.9,
20.1, 122.7, 122.8, 126.0 (2C), 126.2, 128.0, 129.1, 129.3, 139.8, 147.6,
2
3
,
[
f
d
1
hexane) 0.53; H NMR (CDCl
OCH CH
3
, 200 MHz)
d
H15BrO
3
: C, 52.19; H, 5.05.
þ
2
3
2
Found: C, 52.35; H, 4.89; HRMS (ESI) m/z [MþH] for C13
3
H16BrO :
2
2
2
299.0277, found: 299.00273.
13
2
C
3
d
4.2.8.3. 2-((2-Methylallyloxy)methyl)-1-bromo-3,4-dihydro-5,8-
dimethoxynaphthalene (29). Yellow oil; yield 83%; R (4% EtOAc in
1
f